At 08:20 PM 4/24/04 -0400, Anthony Toft wrote:
>I am trying to program a chip, using a Tait style programmer. I have
>recently switched to a 18v/800mA wallwart (measures 24v on the DVM)
>instead of 2 9v batteries. I think this is enough power, I am seeing
>4.5v on Vdd and 13.2v on Vpp.

Questions:
        a) Is the 24V reading with no programmer attached? If so, it's the peak
voltage from the rectifier. "Usually", warts such as that will produce the
rated numbers - if you load it, you are likely to see 18V at 800mA or so.
This ought to be plenty to program with I think.

        b) Only 4.5V and 13.2V??? With the programmer attached? With no chip? With
a chip? ???  With only the programmer attached to the wart, it should be
closer to 18 out of the wart and the programmers 5V line should be 5V.  If
your pic-chip sample causes the drop to 4.5V, it looks like it may indeed
be fried.  If so do yourself a favor and toss it.

        c) Before continuing further, since you have some doubt about your wall
wart, test it with some load resistors.  If testing only with a DVM, you
should realize that there may be significant amounts of ripple.  To test
that theory either measure the output under load with the meter set to show
AC Volts -or- add 1000 or 10,000 uFds or so.  The extra capacitance will
average out the ripple.  You can make your DVM tell the truth if you ask it
nicely!

        d) Once you are sure of the output capabililty of your power supply, then
you can proceed.

        e) Other people will have to add to this as far as the Tait programmer
goes. I no nothing about it.  As far as the programming algorithms are
concerned, you will need to do your homework and look up the specs for each
one and compare them.  Where you say "the datasheet suggests that otherwise
they are identical and meant as drop in replacements" that may refer to
functionality, not necessarily how they program.  If no one else can add to
this, you will need to Read The Fine Manual more thoroughly.  But what a
fun way to spend the weekend, no?

Good luck,
Tom

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